This disclosure relates generally to a radiography imaging technology, and more particularly to a mobile radiography system and aligning method thereof.
Mobile digital radiography (DR) systems are widely used in hospitals. The image quality of mobile DR is usually not as good as fixed DR systems. One major reason is that when using a mobile system, the operator has to manually adjust both x-ray tube and detector. While for fixed system, the detector's position is fixed in most cases. The operator only adjusts the position of x-ray tube, which travels along two or three orthogonal axis. Since the tube and detector are well aligned for fixed systems, anti-scatter grids are used to improve contrast-to-noise ratio of x-ray image. For mobile DR systems, artifacts caused by anti-scatter grids can be found in the x-ray image if the x-ray tube and detector are not well aligned.
In order to align the radiation source and the detector, the radiation source should be aligned to the center of the detector with predetermined distance and the center beam of the radiation source should be perpendicular to the detector. It will be a challenge to align the radiation source and the detector to meet all these three requirements.
There have been a number of approaches to the problem of providing methods and tools to assist operator adjustment of the radiation source and detector. A U.S. Pat. No. 9,179,886 entitled “Alignment apparatus for x-ray imaging system” introduces a method for aligning a radiation source with a portable image receiver in a radiographic imaging system generates a magnetic field with a predetermined field pattern and with a time-varying vector direction at a predetermined frequency from an emitter apparatus that is coupled to the radiation source, wherein the generated magnetic field further comprises a synchronization signal. Sensed signals from the magnetic field are obtained from a sensing apparatus that is coupled to the image receiver, wherein the sensing apparatus comprises three or more sensor elements, wherein at least two of the sensor elements are arranged at different angles relative to each other and are disposed outside the imaging area of the image receiver. An output signal is indicative of an alignment adjustment according to the amplitude and phase of the obtained sensed signals relative to the synchronization signal. This method uses magnetic field technology to retrieve the relationship between a radiation source and a portable image receiver. However, the magnetic field can be easily interfered by the surrounding environment. This method further has drawback of low precision and high cost.
A U.S. Pat. No. 9,055,886 entitled “Automatic tool alignment in a backscatter x-ray scanning system” introduces technologies pertaining to backscatter x-ray scanning systems. This disclosure introduces an alignment method based on the x-ray image. The first x-ray image is captured and region of interest is selected from the image. The proposed system will automatically align the x-ray source and detector and retake a second x-ray image. The drawback of this method is that the patient has to take risks of being exposed with extra dose of X-rays, because second shot of X-ray is required.
Thus, it can be seen that there is a need for an apparatus that enables proper alignment of a radiation source relative to an image detector with optional anti-scatter grid for taking a radiation image.